return spring

[lyndon]

Has anyone fitted a throttle return spring to the alfa engine, as mine will not return to idle once depressed. the cable set up seems smooth enough but when released after depressing the accelerator it revs at about 2500rpm which is a few mm off the stop,
Lyndon.

[chris.richard]

Yes I have. I'll try and post a pic tomorrow. Basically a pillar attached by the bolt that holds the plenum on to the cam cover, and a spring from that to a hole drilled in the black throttle cable circle thingy.
It seems strange that yours doesn't work without an accessory spring. Does it work if you disconnect the cable, or is the intrinsic spring knackered or the movement too stiff? Mine is coz rally regs want 2 throttle closing springs.

[lyndon]

I think it could be the spring on the butterfly assembly but it worked fine in the old 164 . Is it possible to twist the spring another turn or would that be to much to ask
Lyndon.

[chris.richard]

Here's my setup. Sorry about the quality, i have to us my phone coz my digital camera went phut!

[lyndon]

Cheers Chris,
it's a bit different on the 12v but I'll give it a go
Lyndon.

[Stratos]

I have one on my 12v for the same reason as Chris - needed for rallying.

I can't get to the car at present to take a photo for you.

[lyndon]

will wait for the photo Dave as I alway's seem able to over complicate problems when there is often a simple solution,
Lyndon.

[chris.richard]

Different angle

[lyndon]

Dave ,have you been able to take a photo of your throttle return spring yet,
Lyndon.

[Stratos]

I really must apologise to you - I completely forgot about when we out testing last week.

Keith has the car in the workshop on Tuesday, so I'll see if he can take a picture for me.

[lyndon]

cheers David,I have plenty to keep me occupied it's just another thing on my list of things to do,
Lyndon.

[CorseChris]

I think it could be the spring on the butterfly assembly but it worked fine in the old 164 . Is it possible to twist the spring another turn or would that be to much to ask
Lyndon.

I mucked about for a while with mine as it didn't quite return properly sometimes (only a slight rev lift). You can get another half-turn OK, and a full turn with effort, but it's fiddly as heck to do. I tried an extra turn on the built-in spring, then finding that didn't feel very nice, I did the trick of making the throttle quadrant smaller. This does two things - makes the throttle feel more responsive and gives the original return spring more mechanical advantage (or at least less disadvantage) over the drag from the linkage & cable.

Just made up a new quadrant out of a sandwich of 3 ali sheets about 80% the size of the original. If you get it right, you can use the original fixing bolts as well.

[lyndon]

Sounds good Chris , but what difference if any will that make to the pedal travel,
Lyndon.

[Arthur]

Just (well, for about 8 years) had the same problem at the other end of the travel range.
Initially, the cable worked just fine (mine's a Corse I with the 12V alpha lump), although I recall at build having to run it as straight as possible, with minimum number of maximum radius bends I could arrange, or it stuck all over the shop.
Some 12 to 24 months later, I became aware that when cold, the throttle would just ever so slightly stick open at full bore. After a push or two, or the whole thing warmed up, no problem. So I soldiered on for a while. Gradually became worse - the sticking at full bore became more frequent, and started to scare the s**t out of me.
So I fitted a second spring. What I actually did was to pinch the cable length adjuster from an old cable, bolted on a bit of bent ally to the end of the cam quadrant, and if you look down the block, there's a thread hole M6 which got another bit of bent ally. This gave me a fine length adjuster for the cable and a position for the extra return spring. With too heavy a spring, the throttle takes too much push, the car feels leaden and dead. Took a bit to get the additional tension just exactly right, so it doesn't stick open, and reliably closes to the Motronic switch, but it's worth it, and additionally gives belt-and-braces return springing.
What became really noticeable was that a small increase in return spring tension causes much more binding in the throttle cable itself, so if the cable is on the way out, rusty internally, or whatever, just adding another spring may not end your troubles.
A well lubricated cable is an absolute must.

All the best,
Arthur.

[lyndon]

Thanks for that Arthur,
the cable set up is new and well lubricated but I'll look at your suggestion and see if it helps,
cheers ,Lyndon.

[Steve Strain]

Hi Guys

I presume for competition purposes that you must have two return springs on the throttle body, if not the problem could be due to tension in the cable and resistance due to the weight of the pedal mechanism.

It’s just a thought but are you using a floor mounted throttle pedal?
If so the cable path is then relatively short and almost straight following the centre tunnel until it lifts up over the gear box into a gentle curve to the underside of Alfa throttle body. As such there should be little or no resistance in the cable.
On my set up I have used a good quality inner and outer cable from a Motor Bike shop with the Alfa ends re-attached. The throttle body retains the standard return spring but I have added another to the pedal itself. The reason for this was to add some resistance to the pedal to gain a better feel without adding more tension into the cable. As you have observed without an extra spring somewhere the leverage and weight of pedal mechanism easily overcomes the throttle spring and it doesn’t return fast enough (or at all).
My point is that with a spring at each end, the cable has less tension on it so will work more freely and then you may not need the extra spring on the throttle body itself. I have found it easy enough to play around with differing springs at the pedal end to get the weighting I like without affecting the cable and throttle body operation.

I hope this helps

I also have an adjustable bolt acting as a pedal stop so that in moments of over exuberance no one can push it past full throttle position, snap the cable or bend anything (another story).

Cheers

Steve

[Arthur]

Ah, Yes, absolutely right.
I should add that I use a throttle pedal box supplied by CAE with a pedal return spring fitted - in fact I've changed that as well, cos the original spring didn't pull the pedal to the backstop. But Steve's dead right, get the pedal weight off the cable, then the throttle body quadrant return springs are solely returning the quadrant.
The pedal box, as with Steve's set-up, has bolts at min and max positions to set the pedal travel with dead stops and prevent overtension of the cable.

Arthur.

[CorseChris]

Sounds good Chris , but what difference if any will that make to the pedal travel,
Lyndon.


Reduces the total throw pro-rata with the reduction, but I find it still feels nice. I'm using a home-made pedal assembly so YMMV depending on the ratios you already have.

Wholeheartedly agree with the idea of having a return spring on the pedal though - something I need to sort out myself, is that.

[rutthenut]

I fitted a second throttle return spring to my car when first built, since it is 'good practice; in the first place and also, it is required for MSA rules.

With the 12V Alfa engine, there is a small tab on the throttle quadrant, which I seem to recall is used for the idle setting screw. I drilled a small hole through that and ran a spring from there to a small tab that I fixed to one of the plenum chamber/rocker cover mounting bolts.

Same approach worked on the 24v engine, although I think the quadrant is slightly different. Will try and take a pic for you if you it helps at all.

Important to get a decent spring for this purpose. I used what were described as 'Mini throttle springs'; these have a 'bullet' shape to the spring itself, with a wire loop coming out from the spring centre. Think you'll find similar types on Weber throttle linkage kits and the like.

[carlsberg]

just to carry on the thread I have had the same problem as you in the past trying all sorts of things including springs at each end of the cable.
in the end to solve the problem and to give a light and responsive throttle pedal with the merest hint of a second return spring to satisfy the scrutineers at rallies, i changed my complete inner and outer cable for a VENHILL cable......... superb and full throttle without effort or worry that it is going to stick

regards
chris